How to Stop Car Windows from Fogging Up

Windshield Condensation always happens when you are in a hurry, jumping into your car or truck when you are late for work, or picking up the kids. So you drive off without being able to completely see. It could lead to a dangerous situation. It happens in all seasons of the year especially when it’s raining. How do I stop my car windows from fogging up?

Crack car windows
Turn Defrosters on high
Air Recirculation off
Turn heat off
Turn AC on
Keep windows clean
Buy anti-fog spray cleaner

Turn on Heater’s highest setting
Then turn AC on
Air Recirculation off
Let’s some hot air in from outside to balance temp.
Keep windows clean
Buy anti-fog spray cleaner

There are optimal settings in all seasons and weather conditions and Manual Climate Control vehicles that still need to be set by the owner.

Condensation On Glass


Condensation is the process where water vapor becomes liquid. All air carries some amount of water vapor. In weather the more humidity in the air the more water vapor it is carrying and when the air is at 100% humidity it spills over into droplets that are called Condensation. It’s the reverse of evaporation, where liquid water becomes a vapor. It can happen in two ways

  • Either the air is cooled to its dewpoint
  • It becomes so saturated with water vapor that it can’t hold any more water

Dew Point-Dew is condensed water in the atmosphere. The Dew Point is the temperature where the condensation happens. Air temperature can reach or fall below naturally as they do at night time. You’ll see lawns and cars covered with water droplets in the early morning hours. Simply put, when warm air hits cold surfaces like glass, water condensates and fogs your windshield.

It’s all about the difference between the temperature of air and the temperature of the glass. A cold can of beer or shower mirrors sweat droplets of water covering the can on a summer’s day because the difference in temperature helps create elevated moisture levels.

In the morning, there is no time to clear condensation from your car windows, especially during the workweek. This can leave you in a compromising situation and maybe an even dangerous one. During cold weather, turning the heat off inside your car may also cause moisture to build upon your windshield or windows.

That’s also why on warm, humid days, condensation may form at the base of a windshield, where outside air encounters cooled air from the car’s air conditioner. Generally speaking, when warm air meets cold air, moisture develops on surfaces. When the surface is a window, it fogs up. Even a person’s breath that is warm and carries moisture can fog up your windows in a cold car. This can obstruct your view.

Car Windows Fogging Up Outside


When the temperature and moisture level increase outside (Summer) and are greater than inside the car, moisture will condense on the exterior of the car glass. Similar to the situation when it’s colder outside than the inside of your car, the goal is to regulate and balance the two.

  • Turn the heat to its maximum setting, because hot air can hold more moisture
  • Then, turn the AC on, which will pull the moisture from the air as it passes over the cooling coils. AC units like the ones at home work like dehumidifiers and pull moisture from the air in the vehicle.
  • Leave Air Recirculation off: it’s a good idea to turn off your car’s recirculation feature to battle foggy windows so the temperature and moisture levels in your car begin to equalize with those outsides. Cold air does not have the capacity to hold water vapor as hot air does. So it will be a little uncomfortable for awhile
  • Let outside air in to balance out your car’s temperature.   Even if you know it’s hot outside, letting the warm air outside come into your car to remedy this problem can be a quick fix. This quick blast of warm air is a lot better than turning your car’s heat on during those 90-degree nights.


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How To Defog Windshields in The Winter


During the winter, the opposite effects of Summer Condensation will happen. Condensation builds on the inside of the windshield because the air inside the car is warmer and more humid thanks to your body or other hot beverages and food that you’re picking up than the cold, dry air on the outside of the car.

  • If you are in a hurry, open your car windows or crack them to quickly bring the temperature inside closer to that outside.
  • Turn your heat off, and you’ll notice the fog will disappear very quickly.
  • If it’s too chilly out to open your windows, turn the defroster on high and turn off your air recirculation. You want to allow the moist air inside your car to leave.
  • Turn on AC to pull moisture from the air in the vehicle
  • Keep your windows clean because a clean window fogs up less easily.
  • Purchase an anti-fog spray cleaner to use on the inside of your windows


Why You Should Never Use Straight Antifreeze In Your Car or Truck


  Defogging Your Windshield With Manual Climate Control                                                                              

Internal  Defogging                                                                                                

  • Set the Fan Speed to the highest position
  • Set the temperature to the lowest position
  • Set the Floor/Defrost or the Defrost position
  • The AC will now turn on
  • If the AC does not automatically turn on manually turn it on one
  • Set it to the Fan to the highest position
  • Set the Temperature to the extreme hottest position
  • Set to Defrost
  • The Fresh Air and AC will turn on-if not turned on manually

External Defogging

  • Set the Fan speed to the highest position
  • Set the Temperature to the extreme hottest position
  • Set to The defrost position
  • The fresh air and AC will turn on if not
  • If not-Turn on AC manually

How do I Keep My Windshield from Fogging Up


Wipe the inside windshield down with an ammonia-based window cleaner. You should clean the inside of the window with an ammonia-based window cleaner to remove the buildup of film that commonly emanates from windshields. Rub the solution on the windshield with orderly horizontal or vertical strokes. Check the setting in your vehicle for fresh air and recirculation. The recirculation settings reuse the air already in the car.

You can store Desiccants in the car like Socks filled with kitty litter or collect Desiccant packets that you regularly get from electronic products. Blackboard Eraser is great for wiping windows and windshields. De-fogging by wiping the car windows with a potato. If you don’t want your car smelling like shaving cream, an old sock, and potato then a great product you can get at the Hardware store is Rain X Anti-Fog.

Get some good window cleaner, like a 5-star rated Invisible Glass Cleaner. Rain-X does a windscreen repellent for the outside which rates very high in the auto industry the stuff is excellent. It dramatically increases visibility on those journeys when your windows wiper can’t keep up. By cleaning your windows, you should dramatically reduce the moisture buildup.


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JimGalloway Author/Editor





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